Stay Comfy Blog

Furnace Smells: 4 Culprits and What They Mean

You’ve noticed a funny smell coming from your furnace. What IS it? Is it dangerous? What should I do about it? These are important questions. To determine when to perform maintenance, call your HVAC pro, or call 9-1-1, here are the four most common odors that can come from your furnace and what to do about them.

What’s Normal?

When you first fire up your furnace for the heating season, it’s normal to smell a musty or burning scent. That’s just the system kicking into gear after a season of disuse. Often, it’s simply dust that’s accumulated near the heat exchanger. It normally doesn’t last long — usually no more than a half hour or so — and isn’t anything to be concerned about. However, if it continues, gets worse, or there’s another smell, then see if any of the following apply.

Musty or Dusty Odors

If you’re smelling a persistent dusty or musty odor, try changing your filter. A dirty or clogged filter is often the culprit because it can restrict airflow and cause your furnace to run inefficiently. Throughout the heating season, be sure to check your filter monthly and change it as soon as it shows signs of dust and dirt — it’s the simplest and least expensive way to keep your system running efficiently.

Electrical Burning Smell

A burning odor can sometimes indicate an overheated motor due to wear and tear on various parts. An overheated motor can lead to other problems including an electrical hazard. If this is what you’re smelling, turn off your system and call your HVAC professional. You’ll want them to thoroughly check your system and advise you on any repairs that may be needed.

Chemical Smell

A chemical smell can be caused by a crack in your heat exchanger, which is a serious condition. A cracked exchanger can lead to carbon monoxide leaking into your home. You should call for an emergency inspection of your system by a qualified HVAC professional. And if your carbon monoxide detectors go off, leave your home for fresh air immediately.

Rotten Egg Smell

This odor can occur if you have a gas furnace and could indicate that there’s a gas leak. This is an emergency and you need to have it dealt with immediately. You should leave your home immediately and call 9-1-1 outside. You should also contact your local gas company about the leak. There are inexpensive gas detectors that you can install just like carbon monoxide and smoke detectors to alert you to even small amounts of leaked gas.

Being aware of how your system is functioning, including any odd smells, is your first defense against costly repairs. If you have any concerns about smells or noises or questions about your system’s operation, don’t hesitate to contact your HVAC professional for a full inspection.

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